This invention relates generally to a transporting apparatus and, more particularly, to belt turn conveyors, which extend around a curve.
Belt turn conveyors are used to interconnect generally straight conveyor sections that are aligned in different directions and can provide a turn of up to 180.degree.. Such turn conveyors conventionally include a pair of pulleys, one at each end of the conveyor, and a continuous belt having a smaller length at the inner radius of the turn and a longer length toward the outer radius of the turn. The pulleys and belt are supported by a conveyor frame. The conveyor frame typically includes radially spaced legs and horizontal members connecting the legs, which provide a planar support surface for the upper portion of the belt. In operation, especially when the belt is laden with packages or articles to be transported, the belt experiences radial forces, which tend to pull the belt off the pulleys away from the frame toward the inner radius of the conveyor and to cause the belt to ride off the conveyor frame. Various means are provided to retain the belt on the turn conveyor.
For example, in U.S. Pat. No. 4,955,466 to Almes et al., the conveyor belt is provided with an enlarged distal edge (3), which is captured between upper and lower rollers supported on the conveyor frame. The rollers are angled so that they bear on an inner, downwardly sloping side of the enlarged edge of the belt and make a line contact with the enlarged edge of the belt. Under high speeds of operation, however, the enlarged edge (3) may tend to distort and flatten so that the belt is not adequately restrained in the vertical direction.
In U.S. Pat. No. 5,332,082 to Sommerfield, a conveyor turn is disclosed which includes a plurality of roller assemblies that are secured along the edge of the belt and engage a guide surface provided by a slotted guide rail (31). The vertical movement of the belt is not, however, restrained at its upper portion; instead, the belt is free to lift off the horizontal support member (32) until it makes contact with the free edge of the slotted guide rail. Consequently, the belt may be subject to increased wear and may experience a shortened operational life.
To overcome the problem of belts lifting off their supports, some conveyors have employed two sets of wheels, one set of wheels restrains the belt from sliding off the support and the other set of wheels restrains the belt from lifting off the support. For example, in German Document Patent No. DE 41 13 051 C2 discloses two sets of wheel assemblies. However, the supporting structure, which provide the guide rails for the wheels, is complicated and generally increases the overall height of the turn conveyor. Furthermore, the spacing between the turn conveyor and the adjacent straight conveyor section is increased in order to accommodate the wheels assemblies and the wheel guide rails. When the space between the adjacent conveyor sections is increased, smaller packages may fall between the adjacent conveyor sections or may get caught between the sections. Moreover, with the increase in number of wheel assemblies there is a significant increase in noise.
Therefore, there is a need for a belt turn conveyor which provides means for restraining the belt from lifting off the sliding belt frame while minimizing the space between adjacent belt conveyor sections and the overall height of the belt turn conveyor. Furthermore, there is a need for a belt turn conveyor which provides means for restraining the belt from lifting off the sliding belt frame which will reduce the noise of the conveyor when the belt run conveyor is operation. Moreover, there is a need for a belt that is relatively easy to install and replace.